#include<iostream>
#include<cstdio>
#include<algorithm>
using namespace std;
int n;
bool prime(int n)
{
	for (int i = 2; i * i <= n; i++) {
		if(n%i==0){
			return 0;
		}
	}
	return 1;
}
int main()
{
	cin >> n;
	int ans = 1;
	for (int i = 2; i <= n + 1; i++) {
		if (prime(i)) {
			continue;
		}
		else {
			ans++;
		}
	}
	cout << ans << endl;
	return 0;
}